The present invention relates to a multicontact electrical connector element designed to be mounted on a cable and having means for making an electrical connection between certain conductors of the cable and the cage of said connector element.
Multicontact connector elements are already known, such as those of the ARINC type data interface which are devices comprising:
a metal cage, generally made of nickel-plated aluminum, having a front face and a rear face and defining one or more cells passing therethrough from one face to the other;
one or more insulating blocks received in the cells and each provided with a plurality of through holes extending from one face of the cage to the other; and
individual contacts received in respective through holes of the insulating block.
Each contact is connected to an individual conductor of a cable by crimping, welding, or soldering at the end of the conductor, and it is inserted into a corresponding hole in which it becomes locked by snap-fastening by means of a retaining clip housed in the hole.
In general, such a connector element does not have means for making electrical connections between the conductors of the cable and the cage, and in particular does not have any means enabling the shielding of the cable to be connected electrically to the ground of the cage, unless a grounding piece is provided between the cable and the cage, which piece needs to be secured to the cage.
In ARINC type connector elements, such a grounding piece is a metal bar protected by a conductive coating and which is pressed against the cage by screwing. The grounding bar has orifices within which resilient-finger contacts are inserted by force, and each of these contacts can receive a contact pin mounted at the end of a ground conductor of a cable.
A resilient-finger contact is an assembly constituted by a contact portion proper, also known as a xe2x80x9cthimblexe2x80x9d, which comprises a ring supporting the resilient fingers which are radially deformable, and by a bushing which completely surrounds the thimble to retain it and protect it, particularly while a contact is being inserted by force. The bushing protects the thimble from any stresses that result from inserting the contact by force so as to ensure that the thimble retains its resilient characteristics, in order to enable it to perform its function in reliable manner.
The drawback of such resilient-finger contacts is that while they are being inserted by force into the orifices of the grounding bar, they necessarily damage the coated surface of the grounding bar.
Although such damage is of little consequence under normal conditions of use, it constitutes a real problem when the conductor element is to operate under harsh conditions, in particular in surroundings that are very damp and very salty, since under such circumstances the grounding bar is quickly corroded around the orifices receiving the resilient-finger contacts.
Indeed, such corrosion is accelerated if, as is often the cage, the bar is made of nickel-plated aluminum, and the phenomenon becomes more marked if the resilient-finger contacts are gold plated.
The present invention seeks to provide a novel solution enabling the shielding of the cable to be connected to the ground of the cage.
The present invention provides a multicontact electrical connector element comprising:
a metal cage having a front face and a rear face and defining one or more cells passing therethrough from one face to the other;
one or more insulating blocks received in the cells and each provided with a plurality of through holes extending from one face of the cage to the other;
individual contacts each received in a through hole of the insulating block; and
a grounding piece in electrical contact with the metal cage;
the connector element including the contact portion of a resilient-finger contact inserted directly in the grounding piece, said contact portion being constituted by a ring supporting the radially deformable resilient fingers.
In other words, the invention provides for the contact portion of a resilient-finger contact to be inserted directly in the grounding piece without its protective bushing.
According to the invention, it is advantageous for the grounding piece that is in contact with the cage to be made of bronze.
In addition, the grounding piece can have a thin layer of nickel deposited by electroplating.
Such a layer of nickel performs its conventional function of providing protection against corrosion and presents the additional advantage of being ductile, thereby preventing it from being damaged during insertion of the resilient-finger contact portions, and guarantees better resistance to corrosion over time, even under extremely damp conditions.
Furthermore, if the grounding piece is made of bronze, any local damage to its plating will not give rise to the consequences described above since the copper-nickel electrochemical couple presents low oxidation-reduction potential.
In a particular embodiment of the invention, the grounding piece in contact with the cage is constituted by the cage itself, which cage is provided with orifices for receiving the resilient-finger contact portions.
In another embodiment of the invention, the grounding piece in electrical contact with the cage is a grounding bar provided with orifices receiving the resilient-finger contact portion.
In another embodiment, the cage has a peripheral collar and the grounding piece forms a frame which surrounds the cage and which bears against its peripheral collar.
In another embodiment of the invention, a grounding plate pierced by orifices receives the resilient-finger contact portions and thus acts as the grounding piece. This grounding plate is pressed against the collar of the cage and is thus electrically connected thereto.
In all cases, a second grounding piece which may be in the form of a bar, a frame, or a plate, and which may be conductive or otherwise, covers the grounding piece to hold the retaining clips which serve to snap-fasten the contact pins inserted in the resilient-finger contact portions.
In a particular embodiment, each orifice formed in the grounding piece to receive a resilient-finger contact portion is surrounded by at least one recess which leaves the equivalent of a cylinder of material between said orifice and the recess(es), thereby reconstituting the protective bushing missing from the resilient-finger contact.
This recess can be constituted by a cylindrical groove formed in the surface of the grounding piece providing it is sufficiently thick, or by holes passing through the entire thickness of said grounding piece and separated by bridges of material.